PT91899B - A Bifasic process for the preparation of polymorphous, elastomeric and unsaturated polyamides of asymmetric addition and their use in the manufacture of tires - Google Patents

Abstract

The object of the invention was to provide novel stellate rubbers which have a tan delta curve having the broadest possible vibration- attenuation range. <??>Novel, unsaturated, elastomeric, asymmetrically coupled block copolymers of the general formula (A)n-X-(B)m have now been found which are obtainable by two-pot polymerisation and subsequent coupling. <??>The novel block copolymers are suitable for the production of high-quality tyre components. <IMAGE>

Description

DESCRIPTION

BIPhasic Process for Obtaining Asymmetric Addition, Block, Elastomeric and Unsaturated Copolymers, and Their Use in Tire Manufacturing

The subject of the invention deals with new block copolymers, with asymmetric addition, a two-phase process for obtaining and using them in the manufacture of elements for making tires.

It is well known that the properties of a rubber are essentially determined by the course of the tan delta curve. It is also known that a large amplitude peak in the tan delta curve has a beneficial effect on a series of antagonistic properties of rubber, such as increased skid resistance, decreased heat formation dynamics and decreased rolling resistance, no wear reduction, while taking into account the use during all seasons.

In the past, there have been several attempts to develop rubbers with a high level of properties.

In order to find the most advantageous balance possible between the partially contradictory properties, mixtures of various types of rubber were used.

Another hypothesis for such a solution was to produce copolymers from two different blocks.

Thus, copolymers are known which differ by the type of their chemical composition and / or by their structural construction. As an example, mention should be made of block copolymers of styrene-butadiene, whose blocks A and B differ by their percentage of styrene and / or vinyl.

Such copolymers behave relatively poorly with respect to transformation technology.

Another possibility to influence the properties of rubber and, in particular, the improvement of the cold flow, consists of the addition of the so-called active polymers, existing at the end of the polymerization, with polyfunctional adding agents, such as polyhalides or aromatic polyalkenyl compounds.

However, the yield of the addition, that is, the percentage of products added in relation to the total amount of polymers, is often quite low.

Through this principle, addition products are always obtained, whose ramifications - in terms of molecular weight, composition and structure - are identical.

Although addition products with different branches are basically known, these products nevertheless often contain blocks composed of styrene or butadiene units.

In addition thermoplastic additives with different branches are known.

So far, there is no indication that these products could find use in the tire industry.

For example, US-PS 4 248 983 describes thermoplastic and branched block copolymers of the general formula (A - B / A ') _m - X - (A' / B) _n containing 60 to 95% styrene and 40 to 5% of a conjugated diene.

In the general formula, A means a non-elastomeric polymer segment, which contains 80 to 90% styrene. A '/ B and B / A' mean elastomeric polymer segments based on styrene and a conjugated diene. These products are obtained by polymers

rerisation of the non-elastomeric segment A, addition of an initiator, continuation of the reaction by polymerizing a mixture of styrene and a diene and, finally, by carrying out an addition. Similar block copolymers are known from US-PSS 4 180 530, 4 221 884 and 4 248 980 through 4 248 984.

US-PS 4,391,949 describes coating compositions based on branched-form block copolymers of the general formula (A - B) _x - Y - (C) _z

Here Y is an addition agent, A the polymer of a monovinyl aromatic compound, therefore, for example, a polystyrene block, and B and C are polymers of conjugated dienes, for example, polybutadiene blocks.

The two polymers A - B and C are obtained primarily in two separate reactors. Next, the contents of both reactors are mixed, and the addition agent is added.

All block copolymers have at least one of the following defects:

1. - Block copolymers do not satisfactorily meet the most qualified requirements regarding their use as material for tires.

2. - Problems arise regarding the compatibility of the two blocks.

3. - The tan delta curve has only a small damping maximum.

The aim of the invention presented here is to provide modern, branched-shaped rubbers, which are distinguished by a tan delta curve with the widest possible amplitude of vibration damping.

A new principle of interconnection between rubbers has now been found, through which it is possible to obtain significantly wider tan delta curves (see FIG. 1).

As is well known, in this way, the properties of rubbers can have a positive influence, and the tire industry professional has at his disposal a new parameter for the optimization of rubber properties. In addition, the new rubbers are distinguished by the known advantages of added rubbers (compare EP-OS 0 090 365), as well as rubbers with a high percentage of vinyl (KH Nordsiek, KM Kiepert, rubber and rubber, synthetic materials 35, 371 (1982)). The styrene-containing rubbers have a statistical distribution of the styrene units. The percentage of block polystyrene is below 2%.

biphasic process for obtaining the new rubbers, which is part of this invention presented here, guarantees a high addition performance.

object of the invention is the process of obtaining asymmetric addition block, elastomeric and unsaturated copolymers of the general form (A - B) _n - X - (B) _m , based on butadiene, styrene and possibly isoprene. The block copolymer preferably contains 40 to 90% butadiene, 5 to 35% styrene and 0 to 40% isoprene. A and B are different elastomeric blocks. X is the radical of a polyfunctional adding agent. The number m is at least equal to η. The sum of men on the one hand must be at least 3 and on the other hand at most 25. A blocks preferably comprise 40 to 80%, B blocks correspondingly 60 to 20% of all blocks of the block copolymer. The A blocks are preferably made up exclusively of butadiene units, whose percentage of vinyl groups is between 8 and 60%. B blocks are composed of 0 to 60% of butadiene units, at least 10% isoprene units and a maximum of 45% styrene units. The percentage of vinyl and 3,4-isopropenyl groups - referred to the block

B - is between 75 and 90%.

The object of the invention is also to obtain new block copolymers through a biphasic process, by polymerizing the monomers in an inert organic solvent in the presence of a monofunctional lithium compound. This process consists of obtaining blocks B and C, independently of each other and in two containers, mixing the contents of the reactors and then adding them. It is advisable to add a cocatalyst in the polymerization of block B.

In the process presented here, the vast majority of asymmetric addition block copolymers are produced, according to the invention. In principle, symmetric addition block copolymers may also result from the process in question. However, the applicant's investigations have led to the conclusion that the percentage of these products is very small. For this reason, asymmetric addition products are always referred to in the present invention.

object of the present invention differs from the object of the patent application, filed on the same day and from the same applicant, under the title Single-phase process for obtaining asymmetric addition block, elastomer and unsaturated copolymers, and their use in the manufacture of tires, mainly by the following points;

1. - The block copolymer, according to the invention, has the formula (A) _n - X - (B) _m , unlike that of the block copolymer of the aforementioned patent application (A - B) _n -X - (B ) _m .

2. - The block copolymers, according to the present invention, are obtained, according to claim 5, through a two-phase process, while the copolymers of said application are obtained by a single-phase process.

Then proceed to a detailed description of the process.

As an reaction medium, an inert organic solvent is used. In particular, hydrocarbons having 5 to 12 C atoms, such as pentane, hexane, heptane, oethane and decane, as well as their cyclic analogues, are suitable.

Aromatic solvents, such as benzol, toluol, xylol, among others, are also suitable.

Naturally, mixtures of the solvents mentioned above can also be used.

As a catalyst, alkyl lithium compounds are used, which are easily accessible by reacting lithium with the corresponding alkyl halides. Alkyl radicals have 1 to 10 C atoms. Isolated hydrogen atoms can be replaced by phenyl radicals. Most suitable are the following alkyl lithium compounds: methyl lithium, ethyl lithium, pentyl lithium; preference is given to n-butyl lithium.

The catalyst is added at the beginning of the polymerization of block A and block B.

The type and quantity of the catalyst is generally chosen so that the block copolymer obtained has the following properties:

Mooney Viscosity 100 ° C, DIN 53 523): 35 to 120;

Inhomogeneity U = (Mw / Mn) - 1, determined through gel permeation chromotography (GPC analysis): 0.6 to 4.0;

Defo elasticity (80 ° C, DIN 53

514)

In the process presented here, block B is obtained in the presence of a cocatalyst. In this case, the objective is to obtain

numbers with the highest possible percentage of structural units 1,2 and / or 3,4

R

- CH? - CH - and / or - CH? - C I I

CR CH ^II II ch ₂ ch ₂

R - H (butadiene)

R ~ CH3 (isoprene)

The choice of cocatalysts therefore depends on their ability to keep the tips of the polymers active and to regulate the microstructure, that is, to conduct the course of polymerization with a view to forming the most complete possible structural units 1,2 and / or 3 , 4.

Appropriate cocatalysts cover

- ethylene glycol dialkyl ethers, whose alkyl groups have up to 4 C atoms each, such as ethylene glycol diethyl ether (DEE).

Preference is given to ethers of the general formula * 3

Rl - O - CH - CH ₂ - O - R ₂ where and R ₂ are alkyl radicals with a different number of C atoms of the methyl, ethyl, n- and iso-propyl group, as well as n-, iso-, sec .- and tert.-butyl, and R3 means hydrogen, methyl or ethyl.

Preferably, the sum of the C atoms of the two radicals Ri and R2 is 5 to 7, namely 6. An especially suitable ethylene glycol ether is the compound with = ethyl, R2 = tert.-butyl and R3 = H. glycol ethers are accessible, for example, through the principle of Williamson synthesis, from a sodium alcoholate and an alkyl halide. The ethers of the formula

Rl - 0 - CH - CH ₂ - 0 - C (CH3) 3 can be obtained easily, through the reaction of the corresponding alcohol

Rl - 0 - CH - CH2 - OH with isobutene in the presence of an acid ion exchanger.

The cocatalyst is used in a ratio of 2: 1 to 30: 1, namely 2: 1 to 15: 1, referring to the number of moles of the catalyst.

In the event of higher temperatures, greater quantities of cocatalyst are generally required in order to achieve the desired regulation of the microstructure. Reaction temperatures of 100 ° C must not be exceeded. It is also possible to work with the temperature rising or falling; however in this case it is necessary to take care that the microstructure is not altered in its essentials.

In the production of block A, the amount of the cocatalyst present depends on the desired percentage of vinyl groups.

In the production of block B, styrene is added as a comonomer. With appropriate measures, it is necessary to ensure that the percentage of polystyrene blocks does not exceed 2% by mass. A process for determining the percentage of polystyrene blocks is indicated in the) standardized work by Houben-Weyl Methods of Organic Chemistry volume 14/1 (1061), page 698.

It is known that some compounds, proposed as cocatalysts, have the property of suppressing the formation of polystyrene blocks. The same property has compounds called randomizer, which are mostly potassium salts of alcoholates, as well as organic long-chain carbonic and sulfonic acids. When the randomizer effect of cocatalysts is not enough, they can be added (/ 4/13 randomizer.

Suitable addition agents are polypoxides, such as epoxy linseed oil, polyisocyanates, polyketones, such as 1,3,6-hexanthrione, polyanhydrides, such as pyromelitic acid dianhydride, and dicarbonic acid esters, such as adipic acid dimethyl ester. Classically appropriate are

- the tetrahalides of the elements Si, Ge, Sn and Pb, mainly SÍCI4,

- organic compounds of the general formula R _n / SiHal3 / _n , with η = 1 to 6, mainly η = 1 and 2. Here R is an organic radical with the value n, for example an aliphatic, cycloaliphatic or aromatic radical with 6 up to 16 C atoms. Examples include 1,2,4-tri (2-trichlorosilyl-ethyl) ^1- cyclohexane, 1,8-bis (trichlorosilyl) -octane and l- (trichlorosilyl) - octane,

- organic compounds that contain, at least once, the> SiHal2 group, for example, dimethyl-silyl-chloride,

- hydrogens of the alogen-silane of the general formula Si (H) _m (Hal) 4_ _m with 3 - m - 1,

- di- and trivinylbenzols such as 1,4-divinylbenzol.

As an addition agent, divinylbenzol is preferred.

- 14 Ο The process can be triggered either continuously or continuously.

With the help of the tan delta curve, the professional is able, through variations in the reaction conditions, to obtain block copolymers, which can be used for the manufacture of tire treads with the desired combinations of properties.

If used for vulcanizing, the amorphous polymers obtained are mixed with active and reinforcing diluents, a vulcanizing agent and usual additives. In general, it is necessary to carry out this mixing under the influence of cutting forces.

Masses for the manufacture of tire treads are generally / molded in order to obtain rough treads. In homogenization and molding, which for example can be carried out in an extruder, the temperature and time conditions are selected in such a way that vulcanization cannot be carried out.

The rubber component in the vulcanizable masses preferably consists of more than 70 and in particular 100% by weight of a block copolymer according to the invention and 0 to 30% by weight of a known amorphous rubber for all purposes, as for example, styrene rubber15

-butadiene, 1,4-cis-poly-butadiene, 1,4-cis-poly-isoprene and natural rubber. If preferred, the percentage of rubbers for all purposes can be substantially increased.

Active thinners and reinforcers are, for example, soot from tire tread of various types, possibly highly dispersed silicic acids and their mixtures, treated with silane.

Typical vulcanizing agents contain, for example, sulfur in combination with accelerators. The amount of the vulcanizing agent depends on the remaining components of the vulcanizable mass and can be determined through simple guiding tests.

) As additives, the usual plasticizers used in rubber technology, preferably aromatic, aliphatic and naphthenic hydrocarbons, as well as usual auxiliary agents, such as zinc oxide, stearic acid, resin acids, protection against aging and ozone protection waxes.

Block copolymers, according to the invention, are suitable for the manufacture of tire treads for cars and

- 16 trucks, both for the manufacture of new tires and for the retreading of used tires.

Tire treads are distinguished, inter alia, by the following advantageous properties:

- high skid resistance in wet conditions

- high resistance to friction

- low rolling resistance and therefore low fuel consumption

- high wear resistance

- properties that are maintained for all weather conditions.

As a solvent, a hydrocarbon mixture was used, which consisted of 50% hexane. Other components of this hydrogenated Cg mixture were, in particular, pentane, heptane and octane as well as their isomers. The solvent was dried over a molecular filter with a porosity of 0.4 nm, so that the percentage of water decreases below 10 ppm and was then mixed with N2.

The organic compound of lithium was n-butyl lithium, which was used, if there is no indication in a different direction, in the form of a solution of 20% by weight in hexane.

- 17 24 hours before being used, the isoprene and styrene monomers were cooked through calcium hydride and under recycling, distilled and titrated with n-butyllithium in the presence of 0-phenanthroline.

The glycol ethers were distilled through calcium hydride and then titrated with n-butyl lithium in the presence of o-phenanthroline.

divinylbenzol (DVB) is a mixture of m- and p-divinylbenzol and was used in the form of a 64% hexane solution. The determination of the yield of the addition was carried out insofar as the percentage of the solid matter was determined after evaporating the solvent and the monomers.

The tan delta curves were registered using a torsion pendulum according to Schmieder-Wolf and according to DIN 53 520.

The yield of the addition is considered to be that percentage of rubber, which after reaction with an addition agent has a branched structure and is distinguished from the rubber not added by a considerably higher molecular weight.

The determination is made through GPC analysis, in which tetrahydrofuran is used as a solvent and polystyrene

V as support material. Polymers are identified using a light diffusion detector. For this purpose samples are taken from the reactor before adding the addition agent and at the end of the reaction. Defo hardness (DH) and Defo elasticity (DE) are determined using standard measurement methods (DIN 53 514).

Parts mean parts by mass, percentage (%) means% by mass.

COMPARISON EXAMPLE A

In a first V2A autoclave with a stirrer, rinsed with dry nitrogen, 392 parts of hexane and 67 parts of 1,3-butadiene were placed.

It was then heated to 50 ° C and titrated with a 5% solution of n-butyllithium in hexane under thermoelectric control.

Polymerization was initiated at 50 ° C by the addition of 0.051 parts of n-butyl lithium. The temperature was kept constant by refrigeration, and the base solution was completely polymerized.

At the same time, they were placed in a second V2A reactor of

- 19 identical mode 261 parts of hexane, 33 parts of isoprene and 0.83 parts of 1-ethoxy-2-tert-butoxy-ethane, titrated and polymerized at 50 ° C using 0.030 parts of n-butyl lithium.

Next, the contents of the second reactor were added to that of the first reactor, without the active tips being damaged. Then 0.79 parts of DVB were added. After one hour at 50 ° C, it was cooled to room temperature and 0.5 parts of 2,2 ¹ -methylene-bis- (4-methyl-6-tert-butylphenol) added. The obtained rubber was precipitated through a mixture of isopropanol and methanol in a volume ratio of 80:20 and dried for 24 hours at 70 ° C in a circulating air drying oven.

EXAMPLE

In a first V2A autoclave with stirrer, rinsed with dry nitrogen, 357 parts of hexane and 61 parts of 1,3-butadiene were placed. It was then heated to 50 ° C and titrated with a 5% solution of n-butyllithium in hexane under thermoelectric control. Polymerization was started at 50 ° C by the addition of 0.048 parts of n-butyl lithium. The temperature was kept constant by refrigeration, and the base solution was completely polymerized.

- 20 Τ '

At the same time, 238 parts of hexane, 15 parts of isoprene, 15 parts of styrene and 9 parts of butadiene-1.3 and 0.76 parts of 1-ethoxy-2-tert were placed in a second V2A reactor. -butoxy-ethane, titrated and completely polymerized at 50 ° C with 0.027 parts of n-butyl lithium.

Then, the contents of the second reactor were added to the first reactor in such a way that the active tips were not damaged. Then 0.72 parts of DVB were added. After one hour at 50 ° C it was cooled to room temperature and 0.5 parts of 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol) added. The obtained rubber was precipitated through a mixture of isopropanol and methanol in a volume ratio of 80:20 and dried for 24 hours at 70 ° C in a circulating air drying oven.

TABLE: Composition of block copolymers

Butadiene Isoprene Styrene Example 1.4 trans 1.4 cis 1.2 3.4 1.4 THE 35 27 8 27 3 - 1 32 26 12 11 2 17

- 21 TABLE: Macrostructure of block copolymers

Example UD _K 2) THE 2.9 60 1 2.6 80

1) U = Inhomogeneity

2) K = Yield of addition

Both comparison example A and example 1 describe the obtaining of asymmetric substitution block copolymers. The drawing demonstrates that only block copolymers containing styrene, according to example 1 of the invention, give rise to the desired wide tan delta curves.

LISBON, OCTOBER 3, 1989

Claims (2)

12.- Biphasic process for obtaining asymmetric addition block, elastomeric and unsaturated copolymers, and their use in the manufacture of tires, of the general formula (A) _n -X- (B) _m , based on butadiene and, possibly isoprene, characterized by - To be an elastomeric block, different from B, - X is the radical of a polyfunctional adding agent, and - in order for the following relationships to be valid: (m - n) 0 3 is (m + n) ^ 25. 22.- Biphasic process for obtaining asymmetric addition block, elastomer and unsaturated copolymers, and their use in the manufacture of tires, according to claim 1, characterized in that the block copolymers contain 40 to 90% butadiene, 5 to 35% styrene and 0 to 40% isoprene. 32.- Biphasic process for obtaining asymmetric addition block, elastomeric and unsaturated copolymers and their use in the manufacture of tires, according to claim 2, characterized by the blocks To make up 40 to 80% of all blocks and B blocks 60 to 20% of all blocks. 42.- Biphasic process for obtaining asymmetric addition block, elastomeric and unsaturated copolymers, and their use in the manufacture of tires, according to claims 2 and 3, characterized by the blocks To consist exclusively of butadiene units with 8 to 60% evenly distributed vinyl groups, and blocks B consist of 0 to 60% butadiene units, at least 10% isoprene units and at most 45% styrene units and, the diene units have 75 to 90% vinyl. 52.- Biphasic process for obtaining asymmetric addition block, elastomeric and unsaturated copolymers, and their use in the manufacture of tires, according to claims 1 to 4, through the polymerization of monomers in an inert organic solvent in the presence of an monofunctional lithium compound, characterized by producing blocks A and B independently of each other, by mixing the contents of the reactors and then adding an addition agent. 62.- Biphasic process for obtaining asymmetric addition block, elastomeric and unsaturated copolymers, and their use in the manufacture of tires, according to claim 5, characterized in that in the polymerization of block B a cocatalyst. add